import java.util.Scanner;

public class Main 
{
  
	public static void main (String[] args){

	Scanner w = new Scanner(System.in);
	int a,b,c,d,e;
    a = w.nextInt();

	b = w.nextInt();

	c = w.nextInt();

	d = w.nextInt();

	e = w.nextInt();
	RR rr = new RR();
	double dd = rr.fun(a,b,c,d,e);
	System.out.printf("%.2f",dd);

	w.close();
	}

}

class RR{

	double z;

	public double fun (int a, int b, int c, int d, int e){
	z = (a+b+c+d+e)/5;

	return z;

	}
}